The present invention relates to starters for gas discharge lamps, and in particular to a starter assembly having a magnetic switch for starting a lamp. Traditionally, gas discharge lamps used a special starter switch mechanism to start the lamp. When the lamp is first turned on, electricity flows through a bypass circuit and across a starter switch and through the lamp electrodes. This electricity preheats the electrodes, ionizing the gas in the lamp, thereby creating an electrically conductive medium. After the electrodes are heated sufficiently, the starter switch opens, causing the lamp ballast to provide a voltage surge, and the electric current to arc through the gas discharge lamp. The conventional starter switch uses a small discharge bulb containing neon or some other gas. The bulb has two electrodes positioned adjacent to each other. Current arcs between the electrodes, causing a small amount of heat to build within the bulb, which causes one bimetallic electrodes to bend so that it makes contact with the other electrode. When the two electrodes make contact, the current no longer arcs between the electrodes. Consequently, there are no charged particles flowing through the gas. Without the heat from the charged particles, the bimetallic electrode cools, bending away from the other electrode. This opens the circuit, causing the ballast to transfer energy to the lamp electrodes, and subsequently causing the lamp to ignite. When the current flows through the bypass circuit, it establishes a magnetic field in part of the lamp ballast. This magnetic field is maintained by the flowing current. When the starter switch is opened, the current is briefly cut off from the ballast. The magnetic field collapses, which creates a sudden jump in current causing the ballast releases its stored energy and light the gas discharge lamp.
Other gas discharge lamps rely on a design that does not include a starter switch. Instead, the lamp's ballast constantly channels current through both electrodes. This current flow is configured so that there is a charge difference between the two electrodes, establishing a voltage across the lamp.
Alternatively, gas discharge lamps may rely on a high initial voltage to the lamp electrodes, producing a corona discharge used to start the lamp. Excess electrons on the lamp electrode surface forces some electrons into the gas. These free electrons ionize the gas, and almost instantly the voltage difference between the electrodes establishes an electrical arc.
A first problem with the above starter designs is that they are unable to accommodate variations in lamp preheat requirements. A particular starter must be designed for the preheat requirements of a particular gas discharge lamp or narrow range of gas discharge lamps. A second problem with the above starter designs is that they are unable to adapt to variations in gas discharge lamps caused by variations in lamp materials and lamp construction. These variations can cause a change in the preheat requirements for the lamp. This change may result in a change in the lamp starter design, or a discarding of off-specification lamps. Another problem with the above starter designs is that they are unable to accommodate changes in gas discharge lamp preheat requirements, particularly as these gas discharge lamps change with use and age. The starter assembly of the present invention overcomes, or minimizes these, and other problems associated with conventional gas discharge lamp starters.